The present invention relates generally to a valve for providing pressure relief in response both to attitude and pressure conditions, and relates more particularly to such a valve adapted for implantation to relieve intracraneal pressure in treatment of hydrocephalus.
Devices for draining ventricular fluid in cases of hydrocephalus have been available for some time. An early example of such a device is shown in my U.S. Pat. No. 2,969,066, issued Jan. 24, 1961. These devices essentially are pressure responsive valves which open upon the occurrence of a predetermined gradient across the valve to allow flow of cerebrospinal fluid sufficient to lower the ventricular pressure to the desired level.
Existing shunt valves consisting of the single pressure differential type cannot accommodate the great variation of pressure occurring when a patient changes position from horizontal to vertical.
A solution to this problem is provided by the valve assembly shown in my U.S. Pat. No. 4,621,654, issued Nov. 11, 1986 and in which the valve assembly is responsive both to attitude and pressure. A pressure responsive valve and an attitude responsive valve are disposed in a parallel arrangement which provides an alternate flow path dependent upon the patient's attitude. The pressure responsive valve opens under a relatively high pressure gradient, while the attitude responsive valve opens when the patient is in a substantially horizontal position.
Although the valve disclosed in U.S. Pat. No. 4,621,654 would accomplish its intended purpose, it suffers the disadvantages of being complex in design, requiring a relatively large number of parts and hence being expensive to manufacture. It is also somewhat bulky in size, a distinct disadvantage considering the region of implantation.
The present device due to its novel structure, can be more compact, thereby reducing the likelihood of implant complications such as erosion through the skin, a frequent problem with this type of device. The present valve assembly further comprises a fewer number of pieces then the valve assembly of U.S. Pat. No. 4,621,654 and accordingly is less expensive to manufacture and assemble. In addition, the present valve assembly is more readily made of plastic elements, tending to minimize the interference of the implanted valve with X-ray scanning techniques such as computed tomography.